Method of providing location update messages and paging messages in a wireless communication system

ABSTRACT

The present invention provides a method of operating an idle mobile unit that is capable of communicating with first and second wireless communication systems. One embodiment of the method includes providing a location update message in response to the idle mobile unit transitioning from a first tracking area associated with the second wireless communication system to a second tracking area associated with the second wireless communication system. The first and second wireless communication systems are capable of paging the idle mobile unit following the location update message.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International ApplicationPCT/US2007/061600 filed Feb. 5, 2007, which claims priority to foreignapplication GB 0602403.8, filed Feb. 7, 2006.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to communication systems, and, moreparticularly, to wireless communication systems.

2. Description of the Related Art

Wireless communication systems typically include one or more basestations or access points, which are part of the mobile network, forproviding wireless connectivity to mobile units in a geographic area(such as a cell or sector) associated with each base station or accesspoint. To initiate communication between a mobile unit and a basestation, the mobile unit and the base station must establish a session.For this, the mobile unit attaches to the network, thereby creating inthe network a “UE context” that includes information indicating valuesof various session parameters. UE context information may be transferredfrom one base station (or other network node) to another as the mobileunit moves between the cells, e.g., as part of a handover algorithm.Once a UE context has been established between the mobile unit and thebase station, the mobile unit and the base station may form a wirelesscommunication link, or air interface, which may be used to transmitmodulated radiofrequency signals based on the session parameters. Theair interface includes downlink (or forward link) channels fortransmitting information from the base station to the mobile unit anduplink (or reverse link) channels for transmitting information from themobile unit to the base station. The uplink and downlink channels aretypically divided into data channels, random access channels, broadcastchannels, paging channels, control channels, and the like.

Establishment of the communication session and/or wireless communicationlink is performed according to wireless communication standards and/orprotocols. For example, members of the Third Generation PartnershipProject (3GPP, 3GPP2) establish and agree to standards and/or protocolsthat may then be adopted by service providers for implementing theirwireless communication systems. Adopting the agreed-upon standardsand/or protocols permits service providers to cooperate in providingwireless communication service to subscribers. Examples of current andlegacy wireless communication systems include General Packet RadioSource (GPRS) systems that operate according to the second and/or thirdgenerations (2G and 3G) of the 3GPP standards and/or protocols. The 3Gsystems may also be referred to as Universal Mobile TelecommunicationSystems (UMTS). New standards and/or protocols, such as the Long TermEvolution/System Architecture Evolution (LTE/SAE) standards and/orprotocols, are currently under discussion by the 3GPP.

Mobile units may have an active or an idle wireless communication linkwith one or more base stations. Active communication links are used whenthe mobile unit is actively transmitting and/or receiving informationfrom the base station. When an active mobile unit moves, it may behanded off from a source base station to a target base station. Activemobile units may also be handed off from a source base station to atarget base station when the quality of the wireless communication linkto the source base station falls below the quality of a wirelesscommunication link of a target base station due to changes inenvironmental conditions and/or transmission parameters of the sourceand/or target base stations. In the idle mode, a mobile unit mayperiodically reselect a preferred base station and synchronize to thecorresponding broadcast paging interval. However, the idle mobile unitneed not inform the new base station that it has been selected as thepreferred base station. Thus, states associated with the mobile unit maynot be moved until the mobile unit leaves the idle mode when forwardlink and/or reverse link traffic resumes.

When information becomes available for an idle mobile unit the wirelesscommunication system transmits a paging message indicating that theinformation is available and requesting that the mobile unit enter theactive mode to receive the information. However, as discussed above,idle mobile units are not required to notify base stations when theyhave been selected as the preferred base station. Consequently, thewireless communication system may not know the exact location of theidle mobile unit and therefore may be required to provide pagingmessages to numerous cells or sectors. Conventional wirelesscommunication systems attempt to balance the competing desire to reduceoverhead associated with transmitting location update messages and thedesire to reduce overhead associated with transmitting paging messagesby defining tracking areas that include a plurality of cells or sectorsserved by a plurality of base stations. Idle mobile units may then berequired to transmit a location update message when it crosses theboundary between two tracking areas. Thus, the wireless communicationsystem knows that the idle mobile unit is most likely within thetracking area indicated in the most recent location update message andso may begin the paging processed by providing paging messages via thebase stations within the tracking area.

In the real world, wireless connectivity is provided to mobile unitsusing multiple wireless communication systems, some of which may operateaccording to the most recent standards and/or protocols and some ofwhich may operate according to one or more legacy standards and/orprotocols. For example, the new LTE/SAE wireless communication systemmay be initially deployed by overlaying the system with existing legacy2G/3G/UMTS wireless communication systems. The new and legacy wirelesscommunication systems utilize different radio interface technologiesthat operate according to different standards and/or protocols. Thelegacy 2G/3G/UMTS wireless communication systems are expected to be, atleast initially, more mature than the new LTE/SAE wireless communicationsystems and therefore the legacy wireless communication systems areexpected to provide, at least initially, better and more reliablecoverage. Consequently, mobile units are likely to utilize legacywireless communication systems when coverage from the new wirelesscommunication system is lost or not available.

Transitions between new and legacy wireless communication systems maygenerate a relatively large amount of signaling traffic, at least inpart because both the new and legacy wireless communication systems maydefine overlapping sets of tracking areas. Consequently, the mobile unitmay need to provide two location update messages every time it crosses aboundary between tracking areas associated with the new and/or legacywireless communication systems. For example, if the mobile unittransitions from a tracking area associated with the new wirelesscommunication system into a tracking area associated with the legacywireless communication system, the mobile unit may provide locationupdate messages to both the new and the legacy wireless communicationsystem. The transitions may be the result of movement of the mobileunit, e.g., when a roaming mobile unit crosses a boundary betweencoverage areas of the new and legacy wireless communication systems, orthe result of changing system or environmental conditions, e.g., whenthe channel quality provided by the new and/or legacy wirelesscommunication system changes and triggers a transition between the newand legacy wireless communication systems.

The amount of signaling traffic generated by location update messagesmay also be particularly large when the new wireless communicationsystem is first deployed because the coverage provided by the newwireless communication system may be patchy, resulting in relativelylarge numbers of transitions between the new and legacy wirelesscommunication systems. The number of calls that are dropped by the newand/or legacy wireless communication systems may increase when thesignaling traffic increases. Accordingly, the number of call drops maybe undesirably large when the new wireless communication system is firstdeployed. Furthermore, a tracking area update triggered by a locationupdate message that is transmitted by transitions between tracking areasmaintained by different wireless communication systems results in thesource wireless communication system releasing information (also knownas a context) associated with the mobile unit. This context informationmust be re-created if the mobile unit transitions back to the originalwireless communication system, which may lead to excessive resourceconsumption if the mobile unit frequently flip-flops between differentwireless communication systems.

SUMMARY OF THE INVENTION

The present invention is directed to addressing the effects of one ormore of the problems set forth above. The following presents asimplified summary of the invention in order to provide a basicunderstanding of some aspects of the invention. This summary is not anexhaustive overview of the invention. It is not intended to identify keyor critical elements of the invention or to delineate the scope of theinvention. Its sole purpose is to present some concepts in a simplifiedform as a prelude to the more detailed description that is discussedlater.

In one embodiment of the present invention, a method is provided foroperating an idle mobile unit that is capable of communicating withfirst and second wireless communication systems. One embodiment of themethod includes providing a location update message in response to theidle mobile unit transitioning from a first tracking area associatedwith the second wireless communication system to a second tracking areaassociated with the second wireless communication system. The first andsecond wireless communication systems are capable of paging the idlemobile unit following the location update message.

In another embodiment of the present invention, a method is provided forpaging an idle mobile unit that is capable of communicating with firstand second wireless communication systems. The method may includeproviding a paging message via a first tracking area associated with thefirst wireless communication system and a first tracking area associatedwith the second wireless communication system. The tracking areas areindicated in at least one location update message provided by the idlemobile unit in response to the idle mobile unit transitioning to thefirst tracking area associated with the second wireless communicationsystem.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood by reference to the followingdescription taken in conjunction with the accompanying drawings, inwhich like reference numerals identify like elements, and in which:

FIG. 1 conceptually illustrates one exemplary embodiment of acommunication system, in accordance with the present invention;

FIG. 2A conceptually illustrates a first exemplary embodiment of amethod for providing location update messages, in accordance with thepresent invention;

FIG. 2B conceptually illustrates a first exemplary embodiment of amethod for paging an idle mobile unit, in accordance with the presentinvention;

FIG. 3A conceptually illustrates a second exemplary embodiment of amethod for providing location update messages, in accordance with thepresent invention; and

FIG. 3B conceptually illustrates a second exemplary embodiment of amethod for paging an idle mobile unit, in accordance with the presentinvention.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and are herein described in detail. It shouldbe understood, however, that the description herein of specificembodiments is not intended to limit the invention to the particularforms disclosed, but on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the scope ofthe invention as defined by the appended claims.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Illustrative embodiments of the invention are described below. In theinterest of clarity, not all features of an actual implementation aredescribed in this specification. It will of course be appreciated thatin the development of any such actual embodiment, numerousimplementation-specific decisions should be made to achieve thedevelopers' specific goals, such as compliance with system-related andbusiness-related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time-consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthis disclosure.

Portions of the present invention and corresponding detailed descriptionare presented in terms of software, or algorithms and symbolicrepresentations of operations on data bits within a computer memory.These descriptions and representations are the ones by which those ofordinary skill in the art effectively convey the substance of their workto others of ordinary skill in the art. An algorithm, as the term isused here, and as it is used generally, is conceived to be aself-consistent sequence of steps leading to a desired result. The stepsare those requiring physical manipulations of physical quantities.Usually, though not necessarily, these quantities take the form ofoptical, electrical, or magnetic signals capable of being stored,transferred, combined, compared, and otherwise manipulated. It hasproven convenient at times, principally for reasons of common usage, torefer to these signals as bits, values, elements, symbols, characters,terms, numbers, or the like.

It should be borne in mind, however, that all of these and similar termsare to be associated with the appropriate physical quantities and aremerely convenient labels applied to these quantities. Unlessspecifically stated otherwise, or as is apparent from the discussion,terms such as “processing” or “computing” or “calculating” or“determining” or “displaying” or the like, refer to the action andprocesses of a computer system, or similar electronic computing device,that manipulates and transforms data represented as physical, electronicquantities within the computer system's registers and memories intoother data similarly represented as physical quantities within thecomputer system memories or registers or other such information storage,transmission or display devices.

Note also that the software implemented aspects of the invention aretypically encoded on some form of program storage medium or implementedover some type of transmission medium. The program storage medium may bemagnetic (e.g., a floppy disk or a hard drive) or optical (e.g., acompact disk read only memory, or “CD ROM”), and may be read only orrandom access. Similarly, the transmission medium may be twisted wirepairs, coaxial cable, optical fiber, or some other suitable transmissionmedium known to the art. The invention is not limited by these aspectsof any given implementation.

The present invention will now be described with reference to theattached figures. Various structures, systems and devices areschematically depicted in the drawings for purposes of explanation onlyand so as to not obscure the present invention with details that arewell known to those skilled in the art. Nevertheless, the attacheddrawings are included to describe and explain illustrative examples ofthe present invention. The words and phrases used herein should beunderstood and interpreted to have a meaning consistent with theunderstanding of those words and phrases by those skilled in therelevant art. No special definition of a term or phrase, i.e., adefinition that is different from the ordinary and customary meaning asunderstood by those skilled in the art, is intended to be implied byconsistent usage of the term or phrase herein. To the extent that a termor phrase is intended to have a special meaning, i.e., a meaning otherthan that understood by skilled artisans, such a special definition willbe expressly set forth in the specification in a definitional mannerthat directly and unequivocally provides the special definition for theterm or phrase.

FIG. 1 conceptually illustrates one exemplary embodiment of acommunication system 100. In the illustrated embodiment, thecommunication system 100 includes two wireless communication systems105(1-2) for providing wireless connectivity. The distinguishing indices(1-2) may be used to indicate individual wireless communication systems105(1-2) and/or subsets thereof. However, the distinguishing indices(1-2) may be dropped when referring to the wireless communicationsystems 105 collectively. This convention may also be applied to otherelements shown in the drawings and indicated by a numeral and one ormore distinguishing indices. Persons of ordinary skill in the art havingbenefit of the present disclosure should appreciate that the selectednumber of wireless communication systems 105 is illustrative and thatthe present invention is not limited to systems 100 that only includetwo wireless communication systems 105. In alternative embodiments, thecommunication system 100 may include any number of wirelesscommunication systems 105.

The wireless communication systems 105 operate according to differentradio interface technologies. As used herein, the term “radio interfacetechnology” will be understood to refer to the standards and/orprotocols that are implemented by the wireless communication systems 105to provide wireless connectivity, as well as the hardware, firmware,and/or software that are used by the wireless communication systems 105to implement the standards and/or protocols and provide wirelessconnectivity. In the illustrated embodiment, the wireless communicationsystem 105(1) operates according to a legacy radio interface technology.As used herein, the term “legacy” refers to radio interface technologiesthat operate according to standards and/or protocols that have beenreleased and/or deployed prior to the most current radio interfacetechnology. For example, the wireless communication system 105(1) mayimplement the Second Generation (2G) General Packet Radio Source (GPRS)standards and/or protocols, which have been defined by the ThirdGeneration Partnership Project (3GPP). For another example, a wirelesscommunication system 105(2) may implement the Third Generation (3G) GPRSstandards and/or protocols defined by the Third Generation PartnershipProject (3GPP). The 3G standards and/or protocols may also be referredto as the Universal Mobile Telecommunication System (UMTS) standardsand/or protocols.

The wireless communication system 105(2) operates according to a radiointerface technology that differs from the radio interface technologyimplemented by the wireless communication system 105(1). In theillustrated embodiment, the wireless communication system 105(2)implements the most current (new) radio interface technology. Forexample, the wireless communication system 105(2) may implement the LongTerm Evolution/System Architecture Evolution (LTE/SAE) standards and/orprotocols under discussion by the 3GPP. The new radio interfacetechnology implemented by the wireless communication system 105(2)operates according to standards and/or protocols that may not besupported or recognized by legacy radio interface technologiesimplemented by the wireless communication system 105(1). Similarly, thelegacy radio interface technology implemented by the wirelesscommunication system 105(1) operates according to standards and/orprotocols that may not be supported or recognized by the new radiointerface technology implemented by the wireless communication system105(2).

The wireless communication systems 105 provide wireless connectivity viaone or more base stations 110. However, the present invention is notlimited to providing wireless connectivity via base stations 110. Inalternative embodiments, the wireless communication systems 105 mayprovide wireless connectivity via other entities such as access points,access networks, base station routers, and the like. Each of the basestations 110 provides wireless connectivity to a geographic area or cell115. Although the cells 115 in FIG. 1 are depicted as beingapproximately circular and at least partially overlapping, the topologyof actual cells 115 may be irregular (as well as time varying) and theshapes of the cells 115 may depend upon environmental conditions and thetransmission and/or reception parameters adopted by the base stations110. In one embodiment, the base stations 110 may include directionalantennas that permit the base stations 110 to provide wirelessconnectivity independently and concurrently to one or more sectorswithin the associated cells 115.

The base stations 110 and the associated cells 115 may be used to defineone or more tracking areas. In the interest of clarity and to avoidobscuring the present invention, each cell 115 shown in FIG. 1 isconsidered a tracking area 115. However, persons of ordinary skill inthe art having benefit of the present disclosure should appreciate thatthe present invention is not limited to this specific embodiment. Inalternative embodiments, each tracking area 115 may include more thanone cell associated with more than one base station 115. For example,typical wireless communication systems 100 provide wireless connectivityto tracking areas 115 that include several cells that are served byseveral base stations 110. Accordingly, the base stations 110 andcells/tracking areas 115 shown in FIG. 1 may also be representative ofmore than one base station and associated cell that may form eachtracking area 115.

In the illustrated embodiment, a mobile unit 120 has established asession with the wireless communication system 105(1). For example, themobile unit 120 may have previously initiated the session with the basestation 110(2) and/or another entity in the wireless communicationsystem 105(1), such as a radio network controller (not shown). Themobile unit 120 and the wireless communication system 105(1) may thenhave formed, exchanged, and/or negotiated session establishmentinformation that may be used to establish the session. The sessionestablishment information may also be referred to as a “context.” Forexample, when the wireless communication system 105(1) operatesaccording to 2G or 3G/UMTS standards and/or protocols, the sessionestablishment information includes a Packet Data Protocol (PDP) contextthat may be used to define aspects of the session such as routing,quality of service, security, billing, and the like. The PDP context isa logical association between the mobile unit 120 and a public datanetwork running across a GPRS network, such as the wirelesscommunication system 105(1). Each PDP context includes information suchas an associated PDP address, an access point name (APN) that includesrouting information, a Quality of Service (QoS) for the session, anetwork service access point identifier (NSAPI) that is an index to thePDP context that is using services provided by other layers, atransaction identifier (TI) that is used to distinguish multiplebidirectional message flows for a given connection, and the like. ThePDP context may also be used to establish a radio bearer between themobile unit 120 and the base station 110(2).

The mobile unit 120 is also associated with one or more tracking areas115. For example, the mobile unit 120 may be associated with UTRANregistration area (URA) defined by the 2G/3G standards and/or protocols.The wireless communication systems 105 and the mobile unit 120 maytherefore maintain information that indicates the tracking areas 115that contain the mobile unit 120. For example, the wirelesscommunication systems 105 may include an identifier that indicates thetracking area 115 associated with the mobile unit 120. The trackingareas 115 associated with the wireless communication system 105 mayoverlap, at least in part, so that both wireless communication systems105 may have a record of the mobile unit 120 and the tracking areas 115that include the mobile unit 120. In the illustrated embodiment, thetracking areas 115(1-2) associated with the wireless communicationsystem 105(1) overlap with the tracking areas 115(3-4) associated withthe wireless communication system 105(2). The mobile unit 120 isinitially associated with the tracking areas 115(2-3) and so thewireless communication systems 105 may include information indicatingone or more of the tracking areas 115(2-3) that include the mobile unit120, as will be discussed in detail below. The mobile unit 120 may alsoinclude information indicating the associated tracking areas 115(2-3).

After establishing the session with the wireless communication system105(1) the mobile unit 120 depicted in FIG. 1 enters an idle mode. Inone embodiment, the base station 110(2) may initiate the idle mode bytransmitting a de-registration message to the mobile unit 120. Theserving base station 110(2) may then tear down the traffic channelassociated with the idle mobile unit 120 and release all informationpertaining to the idle mobile unit's network connections. The idlemobile unit 120 may only listen while in the idle mode and can onlyreceive messages from its preferred base station. The media accesscontrol (MAC) state information for the session may also be torn downwhen the mobile unit 120 enters the idle mode, e.g., if the mobile unitexplicitly de-registers its MAC state for the duration of the idlestate. Persons of ordinary skill in the art having benefit of thepresent disclosure should appreciate that the idle modes or statesdescribed in this document may include paging states, such as PacketMobility Management (PMM) Idle, Long Term Evolution (LTE)-Idle, or UTRANRegistration Area (URA)-PCH.

The wireless communication systems 105 may reach the idle mobile unit120 by providing a paging message, e.g., a message indicating thatinformation is available for the mobile unit 120 and requesting that themobile unit 120 move to the active state. For example, an idle mobileunit 120 that is located in a URA and is in the URA-PCH paging state andmay be reachable by paging over a paging channel (PCH).

The idle mobile unit 120 may move or transition between base stations110 and/or tracking areas 115 associated with the different wirelesscommunication systems 105, as indicated by the arrow 125. In theillustrated embodiment, the mobile unit 120 moves from the tracking area115(2) associated with the base station 110(2) in the wirelesscommunication system 105(1) to the tracking area 115(3) associated withthe base station 110(3) in the wireless communication system 105(2). Forexample, the mobile unit 120 may transition from the legacy (2G/3G)wireless communication system 105(1) to the new (LTE/SAE) wirelesscommunication system 105(2). Persons of ordinary skill in the art shouldappreciate that the “move” may be the result of actual movement of themobile unit 120 and/or changing environmental or transmissionconditions. In one embodiment, the transition may result in the mobileunit 120 selecting, or camping on, a new preferred base station 110. Forexample, the mobile unit 120 elect to camp on the base station 110(3)based on a comparison of pilot signal strengths of the base stations110(2-3). Alternatively, the mobile unit 120 may remain camped on thebase station 110(3) even though the transition indicated by the arrow125 results in the mobile unit 120 crossing a tracking area boundarybetween the tracking areas 115(1-2) associated with the wirelesscommunication system 105(1).

The idle mobile unit 120 may provide one or more location updatemessages to one or more of the wireless communication systems 105 toinform the wireless communication systems 105 that it has entered one ormore new tracking areas 115. In one embodiment, the mobile unit 120provides a location update message when it transitions from a trackingarea 115 associated with one wireless communication system 105 to adifferent tracking area associated with the same wireless communicationsystem 105. However, both of the wireless communication systems 105 maywant to be able to page the idle mobile unit and so the location updateinformation is provided in a manner that allows both wirelesscommunication systems 105 to remain aware of the current tracking areas115 for the corresponding systems 105. Both wireless communicationsystems 105 therefore remain able to page the idle mobile unit 120following the location update message. For example, if the idle mobileunit 120 that is initially in a 2G/3G URA-PCH state in the tracking area115(2) and is also in the tracking area 115(3) subsequently camps on thebase station 110(4) in the tracking area 115(4) associated with thewireless communication system 105(2), then the idle mobile unit 120 mayprovide a location update message over the wireless communication system105(2) and remain in the 2G/3G URA-PCH state in the wirelesscommunication system 105(1). For another example, if the idle mobileunit 120 transitions between the tracking areas 115(1-2) while remainingcamped in the tracking area 115(3), then the idle mobile unit 120 mayprovide a location update message via the wireless communication system105(2) that includes identifiers for the tracking areas 115(2-3).

FIG. 2A conceptually illustrates a first exemplary embodiment of amethod 200 for providing location update messages. In the illustratedembodiment, an idle mobile unit, such as the mobile unit 120 shown inFIG. 1, is registered in two wireless communication systems that operateusing different radio interface technologies. For example, the mobileunit may be registered in a first wireless communication system thatoperates according to 2G/3G standards and/or protocols and a secondwireless communication system that operates according to LTE/SAEstandards and/or protocols. In one embodiment, one of the wirelesscommunication systems acts as the proxy for an interface to a homelocation register (HLR). The information from the HLR may then be keptup to date in both wireless communication systems. In the illustratedembodiment, the idle mobile unit is initially camped on a tracking areaassociated with one of the wireless communication systems. For example,the idle mobile unit may initially be camped on a tracking areaassociated with the 2G/3G wireless communication system and thereforemay be in a URA-PCH state. As discussed above, the idle mobile unit mayalso be associated with a tracking area of the other wirelesscommunication system, such as an LTE/SAE wireless communication system.In the illustrated embodiment, both wireless communication systemsretain a context for the idle mobile unit. The wireless communicationsystems also include information indicating the tracking area that wasmost recently reported by the mobile unit to the corresponding wirelesscommunication system.

The idle mobile unit may then camp (at 205) on a new tracking area anddetermine (at 210) whether the tracking area is associated with theoriginal wireless communication system or a different wirelesscommunication system. If the new tracking area is associated with thesame wireless communication system as the original tracking area, thenthe idle mobile unit provides (at 215) a location update message overthe original wireless communication system, which may use the locationupdate message to update the information indicating the current trackingarea associated with the mobile unit. If the idle mobile unit determines(at 210) that it has camped on a tracking area associated with adifferent wireless communication system, then the idle mobile unit mayprovide (at 220) a location update message over the new wirelesscommunication system. For example, if the idle mobile unit thatinitially camped in the 2G/3G wireless communication system camps (at205) on a tracking area associated with the LTE/SAE wirelesscommunication system, and the idle mobile unit may provide (at 220) alocation update message over the LTE/SAE wireless communication system.

In the illustrated embodiment, both wireless communication systemsretain (at 225) their respective contexts for the idle mobile unit.Thus, the tracking area update provided (at 220) over the new wirelesscommunication system does not result in the release of the context inthe other system. Both the mobile unit and the network retain (at 225)full information required for both wireless communication systems. Thelocation update message provided (at 220) over the new wirelesscommunication system also does not change the paging state of the idlemobile unit in the other wireless communication system. For example,mobile units are not taken out of the URA-PCH state in UMTS when thelocation update message is provided via an overlaid LTE/SAE wirelesscommunication system. The idle mobile units may then be paged using bothwireless communication systems because both systems have retained (at225) the context and tracking area identifier that may be used to pagethe mobile unit.

FIG. 2B conceptually illustrates a first exemplary embodiment of amethod 250 for paging an idle mobile unit. In the illustratedembodiment, paging messages are provided (at 255) by to wirelesscommunication systems that operate according to different radiointerface technologies. The idle mobile unit context and/or trackingarea identifiers associated with each of the wireless communicationsystems are used to determine the tracking areas for the page (at 255)of the idle mobile unit. The wireless communication systems thendetermine (at 260) whether a response has been received from the idlemobile unit, e.g. using one or more timers. If no response is received(at 260), then the wireless communication systems may provide (at 255)additional paging messages via other tracking areas that are determinedbased upon the last-reported tracking areas.

If a response to the paging messages is received (at 260), and the idlemobile unit requests establishment of resources for an active sessionwith one of the wireless communication systems, then the wirelesscommunication system that is used to request establishment of resourcesis determined (at 265). The active session is established (at 270) withthe mobile unit over the wireless communication system that was used totransmit the response. For example, if the mobile unit transmitted therequest for resources over the LTE/SAE wireless communication system,then the active session may be established (at 270) with the LTE/SAEwireless communication system. In one embodiment, additional informationmay be transferred to the responding wireless communication system fromthe other system. The context may then be removed (at 275) from thenon-responding wireless communication system. Removing (at 275) thecontext may include a tear down of the resources in the non-respondingsystem, which may lead to a simpler state because the context of theactive mobile unit is only held in one of the wireless communicationsystems. This may also remove dependencies on subsequent handovers. Forexample, if the mobile unit established the bearers in LTE/SAE, theURA-PCH state in UMTS is removed. Persons of ordinary skill in the arthaving benefit of the present disclosure should appreciate that ananalogous method may be used when the active session is formed inresponse to a request from the idle mobile unit that was initiated bythe mobile unit.

In one embodiment, the wireless communication systems may also retainthe mobile unit contexts when the mobile unit is in the active state:Thus, a change over to active in one system does not result in a teardown of resources in the other system. In this embodiment, multiplehandover procedures may be defined depending on the previous states ineach system. For example, if the mobile unit was in URA-PCH in one radionetwork controller (RNC) while in LTE-Active mode and the mobile unitthen moves to a cell in another RNC. Such a handover can be modeled as achange within UMTS from URA-PCH in one RNC to active in another RNC andthe LTE context may be retained in a “dormant” state.

FIG. 3A conceptually illustrates a first exemplary embodiment of amethod 300 for providing location update messages. In the illustratedembodiment, an idle mobile unit, such as the mobile unit 120 shown inFIG. 1, is registered in two wireless communication systems that operateusing different radio interface technologies. In the second exemplaryembodiment, only one system retains the mobile unit context, as well asthe tracking areas for the wireless communication systems. For example,the mobile unit context may be stored in a wireless communication systemthat supported the last active session associated with the mobile unit.The other wireless communication system stores a mobile unit identifierand the tracking areas for the wireless communication systems. When theidle mobile unit is camped in one wireless communication system, mobileunit activity in the other system removes the context in the originalwireless communication system so that the mobile unit context isretained in only one system.

As discussed above, the mobile unit may move or transition betweendifferent tracking areas which may or may not be associated withdifferent wireless communication systems. If the mobile unit detects (at305) that it is in a new tracking area of one of the wirelesscommunication systems, the mobile unit then determines (at 310) whetherthe new tracking area is one of the previously reported tracking areasassociated with the wireless communication systems. If the new trackingarea is one of the previously reported tracking areas, indicating thatthe mobile unit has moved from the previously reported tracking area ofone system into the previously reported tracking area of the othersystem, then no location update message is sent and the mobile unitwaits to detect (at 305) another new tracking area. The mobile unit maytherefore move freely between the two wireless communication systems aslong as it remains within one of the previously reported tracking areas.

If the mobile unit determines, possibly by continuously scanning bothtechnologies, (at 310) that the new tracking area is not one of thepreviously reported tracking areas associated with the wirelesscommunication systems, and the mobile unit provides (at 315) a locationupdate message over the current system. For example, if the mobile unitis camped in a 2G/3G wireless communication system when it enters theURA-PCH or idle state, the mobile unit monitors tracking areasassociated with both the 2G/3G wireless communication system and theLTE/SAE wireless communication system. If the mobile unit determines (at310) that it has entered a new tracking area for the LTE/SAE wirelesscommunication system that is different than the previously reportedtracking area for the LTE/SAE wireless communication system, then mobileunit may provide (at 315) a location update message includinginformation indicating the new tracking area. The location updatemessage may be provided (at 315) using the original system, which in theexample above is the 2G/3G wireless communication system. In oneembodiment, the LTE/SAE tracking area information is passed to the userplane equipment (UPE) or the node where the user context is stored. Thisdoes not necessarily mean that the mobile unit has registered with theLTE/SAE system.

Similarly, if the mobile unit was originally camped in a tracking areaassociated with the LTE/SAE wireless communication system, then themobile unit cannot be in URA-PCH in UMTS since only one system storesthe mobile unit context and, in this example, the mobile unit context isstored in the LTE/SAE wireless communication system. In this case, themobile unit provides the UMTS Routing area over LTE/SAE system. Thus, ifthe mobile unit determines (at 310) that it has entered a new trackingarea for the 2G/3G wireless communication system that is different thanthe previously reported tracking area for the 2G/3G wirelesscommunication system, then mobile unit may provide (at 315) a locationupdate message including information indicating the new tracking area.The location update message may be provided (at 315) using the originalsystem, which in this example is the LTE/SAE wireless communicationsystem.

In one variation of the second exemplary embodiment, continuousbackground scanning in the other technology may be avoided if the mobileunit only checks subsequent LTE/SAE tracking areas when it camps onLTE/SAE. Thus for example, the mobile unit may report the LTE/SAEtracking area when it updates the URA-id over the UMTS wirelesscommunication system. The mobile unit may then be allowed to movebetween the tracking areas in UMTS and LTE/SAE as discussed above. Ifthe mobile unit camps on an LTE/SAE cell that is not the reportedtracking area, then it performs a tracking area update over the LTE/SAEwireless communication system, which may remove the mobile unit contextfrom the 2G/3G wireless communication system.

In one variation of the second exemplary embodiment, a temporaryidentifier may be allocated in both wireless communication systems butcarried to the mobile unit over only one system. For example, thetemporary identifier may be carried to the mobile unit over the sametechnology in which the mobile unit performed the tracking updatesignaling. Thus if the mobile unit is in UMTS URA-PCH state, and itincludes an LTE/SAE tracking area, an LTE/SAE mobile unit identifier isallocated to the mobile unit and carried over the UMTS system itself.When there is a need for paging the mobile unit, the tracking areaidentifier of the respective system can then be used. If keeping themobile unit in URA-PCH all the time is not considered that critical andmobile units can be in PMM Idle, then the UE context to be retained inUMTS is only the SGSN context.

FIG. 3B conceptually illustrates a second exemplary embodiment of amethod 350 for paging an idle mobile unit. In the illustratedembodiment, paging messages are provided (at 355) by to wirelesscommunication systems that operate according to different radiointerface technologies. The idle mobile unit context and/or trackingarea identifiers associated with each of the wireless communicationsystems are used to determine the tracking areas for the page (at 355)of the idle mobile unit. The wireless communication systems thendetermine (at 360) whether a response has been received from the idlemobile unit, e.g. using one or more timers. If no response is received(at 360), and the wireless communication systems may provide (at 355)additional paging messages via other tracking areas that are determinedbased upon the last-reported tracking areas. If a response to the pagingmessages is received (at 360), and the idle mobile unit requestsestablishment of resources for an active session with one of thewireless communication systems, then the wireless communication systemthat is used to request establishment of resources is determined (at365).

If the responding wireless communication system is determined (at 370)to be the same as the wireless communication system that is currentlystoring the context of the mobile unit, then the requested activesession may be established (at 375) over the responding wirelesscommunication system. For example, the requested active session may beestablished (at 375) using system specific procedures associated withthe responding wireless communication system. If the responding wirelesscommunication system is determined (at 370) to be the different than thewireless communication system that is currently storing the context ofthe mobile unit, then the session may be handed off (at 380) to the newwireless communication system. For example, a forward handoff may betriggered (at 380); e.g., by a mobile unit request or paging response inthe other system.

The particular embodiments disclosed above are illustrative only, as theinvention may be modified and practiced in different but equivalentmanners apparent to those skilled in the art having the benefit of theteachings herein. Furthermore, no limitations are intended to thedetails of construction or design herein shown, other than as describedin the claims below. It is therefore evident that the particularembodiments disclosed above may be altered or modified and all suchvariations are considered within the scope of the invention.Accordingly, the protection sought herein is as set forth in the claimsbelow.

The invention claimed is:
 1. A method of operating an idle mobile unitthat is registered with first and second wireless communication systemsthat operate using different radio interface technologies, the methodcomprising: transmitting a location update message in response to theidle mobile unit transitioning from a first tracking area associatedwith the second wireless communication system to a second tracking areaassociated with the second wireless communication system, wherein theidle mobile unit remains associated with a first tracking areaassociated with a first wireless communication system after transmittingthe location update message so that the first and second wirelesscommunication systems are able to page the idle mobile unit, and whereinthe location update message contains an indication of the secondtracking area associated with the second wireless communication systemand an indication of the first tracking area associated with the firstwireless communication system.
 2. The method of claim 1, whereintransmitting the location update message comprises transmitting thelocation update message via the second wireless communication system inresponse to the idle mobile unit selecting a base station in the secondtracking area associated with the second wireless communication system,and the method further comprises: transmitting a request to establish anactive communication link with at least one of the first and secondwireless communication systems; and establishing the activecommunication link with at least one of the first and second wirelesscommunication systems based on a context stored in the first and secondwireless communication systems.
 3. The method of claim 1, whereintransmitting the location update message comprises transmitting thelocation update message via the first wireless communication system inresponse to the idle mobile unit detecting a transition from the firsttracking area associated with the second wireless communication systemto the second tracking area associated with the second wirelesscommunication system.
 4. The method of claim 3, wherein the mobile unitis located in a first tracking area associated with the first wirelesscommunication system that overlaps with portions of the first and secondtracking areas associated with the second wireless communication system,and wherein transmitting the location update message comprises providinginformation indicative of the first tracking area associated with thefirst wireless communication system and the second tracking areaassociated with the second wireless communication system in response tothe idle mobile unit detecting the transition from the first to thesecond tracking area associated with the second wireless communicationsystem.
 5. The method of claim 4, comprising transmitting an additionallocation update message in response to detecting a transition from thefirst tracking area associated with the first wireless communicationsystem to a second tracking area associated with the first wirelesscommunication system, the location update message being transmitted viathe first wireless communication system and including informationindicative of the second tracking area associated with the firstwireless communication system and the second tracking area associatedwith the second wireless communication system.
 6. The method of claim 5,comprising transmitting a request to establish an active communicationlink with at least one of the first and second wireless communicationsystems.
 7. The method of claim 1, comprising transmitting locationupdate messages to the first and second wireless communication systemsin response to the mobile unit entering an idle mode.
 8. The method ofclaim 1, wherein the location update message further comprises anindication of the first tracking area associated with the secondwireless communication system.
 9. The method of claim 8, wherein saidindication of the first tracking area associated with the secondwireless communication system is an identifier included in the locationupdate message.
 10. The method of claim 1, wherein said indication ofthe first tracking area associated with the first wireless communicationsystem is an identifier included in the location update message.
 11. Amethod of paging an idle mobile unit that is registered with first andsecond wireless communication systems that operate using different radiointerface technologies, the method comprising: transmitting a pagingmessage via a first tracking area associated with the first wirelesscommunication system and a first tracking area associated with thesecond wireless communication system, wherein said first tracking areasassociated with the first and second wireless communication systems areboth indicated in a single location update message provided by the idlemobile unit in response to the idle mobile unit transitioning to thefirst tracking area associated with the second wireless communicationsystem.
 12. The method of claim 11, comprising receiving a request toestablish an active communication link with the first or second wirelesscommunication systems, the request being received from the idle mobileunit in response to transmitting the paging message, wherein receivingthe request comprises receiving the request via either the firstwireless communication system or the second wireless communicationsystem, and further comprising: establishing the active communicationlink with the mobile unit using the wireless communication system thatcommunicated the request to establish the active communication link, theactive communication link being established using a mobile unit contextstored on this wireless communication system; and removing a mobile unitcontext stored on the other wireless communication system.
 13. Themethod of claim 12, wherein the idle mobile unit has selected a basestation of the first wireless communication system, and whereinreceiving the request comprises receiving the request via either thefirst or second wireless communication system, and further comprising:establishing the active communication link with the mobile unit over thefirst wireless communication system in response to receiving the requestvia the first wireless communication system; and handing off the idlemobile unit to the second wireless communication system in response toreceiving the request via the second wireless communication system andestablishing the active communication link with the mobile unit over thesecond wireless communication system.
 14. The method of claim 11,wherein the single location update message provided by the idle mobileunit further comprises an indication of a second tracking areaassociated with the second wireless communication system.
 15. The methodof claim 14, wherein said indication of the second tracking areaassociated with the second wireless communication system is anidentifier included in the location update message.
 16. The method ofclaim 11, wherein said indication of the first tracking area associatedwith the first wireless communication system is an identifier includedin the location update message.
 17. A method of operating an idle mobileunit that is registered with first and second wireless communicationsystems that operate using different radio interface technologies, themethod comprising: transmitting a location update message in response tothe idle mobile unit transitioning between tracking areas both of whichare associated with only one of the first or second wirelesscommunication systems, wherein the idle mobile unit remains associatedwith a tracking area that is associated with the other one of the firstand second wireless communication systems and the location updatemessage indicates both of the tracking area transitioned-to and thetracking area associated with the other of the first and second wirelesscommunication systems.
 18. The method of claim 17, wherein transmittingthe location update message comprises transmitting the location updatemessage via the one of the first and second wireless communicationsystems in response to the idle mobile unit camping in a tracking areaassociated with the one of the first and second wireless communicationsystems, and further comprising: transmitting a request to establish anactive communication link with either of the first and second wirelesscommunication systems; and establishing an active communication linkwith a wireless communication system indicated in the request based on acontext stored in the wireless communication system indicated in therequest.
 19. A method of operating an idle mobile unit that isregistered with a first wireless communication system that operatesusing a second generation (2G)/third-generation (3G) radio interfacetechnology and a second wireless communication system that operatesusing a Long Term Evolution (LTE)/System Architecture Evolution (SAE)radio interface technology, the method comprising: transmitting alocation update message in response to the idle mobile unittransitioning between tracking areas both of which are associated withonly one of the first or second wireless communication systems, andwherein the location update message contains at least indications of thetracking area transitioned-to and the tracking area associated with theother of the first and second wireless communication systems.
 20. Themethod of claim 10, wherein the idle mobile unit remains associated witha tracking area associated with the other of the first and secondwireless communication systems after transmitting the location updatemessage.
 21. The method of claim 19, wherein transmitting the locationupdate message comprises transmitting the location update message viathe one of the first and second wireless communication systems inresponse to the idle mobile unit camping in a tracking area associatedwith the one of the first and second wireless communication systems, andfurther comprising: transmitting a request to establish an activecommunication link with either of the first and second wirelesscommunication systems; and establishing the active communication linkwith a wireless communication system indicated in the request based on acontext stored in the wireless communication system indicated in therequest.
 22. A mobile unit configured to transmit a location updatemessage while the mobile unit is in an idle mode, wherein the mobileunit is registered with both of first and second wireless communicationsystems each of which operates using a different radio interfacetechnology, wherein the mobile unit transmits the location updatemessage in response to the mobile unit in the idle mode transitioningfrom a first tracking area associated with the second wirelesscommunication system to a second tracking area associated with thesecond wireless communication system, wherein the mobile unit in theidle mode remains associated with a first tracking area associated withthe first wireless communication system and the second tracking areaassociated with the second wireless communication system aftertransmitting the location update message, and wherein the locationupdate message and indicates the second tracking area associated withthe second wireless communication system and the first tracking areaassociated with the first wireless communication system.
 23. The mobileunit of claim 22, wherein the mobile unit is configured to transmit thelocation update message via the second wireless communication system inresponse to the mobile unit in the idle mode selecting a base station inthe second tracking area associated with the second wirelesscommunication system, and wherein the mobile unit is further configuredto: transmit a request to establish an active communication link with atleast one of the first and second wireless communication systems; andestablish an active communication link with at least one of the firstand second wireless communication systems based on a context stored inthe first and second wireless communication systems.
 24. The mobile unitof claim 22, wherein the mobile unit is configured to send the locationupdate message via the first wireless communication system in responseto the mobile unit in the idle mode detecting a transition from thefirst tracking area associated with the second wireless communicationsystem to the second tracking area associated with the second wirelesscommunication system.
 25. The mobile unit of claim 22, wherein themobile unit is configured to transmit location update messages to thefirst and second wireless communication systems in response to themobile unit entering the idle mode.
 26. The mobile unit of claim 22,wherein the different radio interface technologies comprise a secondgeneration (2G)/third-generation (3G) wireless communication system anda Long Term Evolution (LTE)/System Architecture Evolution (SAE) wirelesscommunication system.
 27. The mobile unit of claim 22, wherein thelocation update message indicates the first tracking area associatedwith the second wireless communication system.
 28. The method of claim27, wherein the location update message indicates the first trackingarea associated with the second wireless communication system using anidentifier included in the location update message.
 29. The method ofclaim 22, wherein the location update message indicates the firsttracking area associated with the first wireless communication systemusing an identifier included in the location update message.
 30. Amobile station for use in an environment in which a mobile station inidle mode is concurrently recognized in both two different wirelesscommunication systems during a period of time, wherein one of saidwireless communication systems uses a second generation(2G)/third-generation (3G) radio interface technology and the other ofsaid wireless communication systems uses Long Term Evolution(LTE)/System Architecture Evolution (SAE), and wherein a mobile stationremains registered in a first tracking area of a first of said wirelesscommunication systems after transitioning while in idle mode from afirst tracking area of a second of said wireless communication systemsto a second tracking area of said second of said wireless communicationsystems, the mobile station being configured to: transmit a locationupdate message upon transitioning from said first tracking area of saidsecond of said wireless communication systems to the second trackingarea of said second of said wireless communication systems, saidlocation update message indicating both the second tracking areaassociated with the second of the wireless communication systems and thefirst tracking area associated with the first of said wirelesscommunication system.
 31. The mobile station of claim 30, wherein saidlocation update message indicates the first tracking area associatedwith the second of the wireless communication systems.
 32. The method ofclaim 31, wherein the location update message indicates the firsttracking area associated with the second of the wireless communicationsystems using an identifier included in the location update message. 33.The method of claim 30, wherein the location update message indicatesthe first tracking area associated with the first of the wirelesscommunication systems using an identifier included in the locationupdate message.
 34. A first base station configured to page an idlemobile unit via a tracking area associated with a first wirelesscommunication system substantially concurrently with paging of the idlemobile unit by a second base station that is part of a tracking areaassociated with a second wireless communication system, wherein thefirst and second wireless communication systems operate using differentradio interface technologies and the idle mobile unit is registered withboth the first and second wireless communication systems, and whereinsaid tracking area associated with the first wireless communicationsystem and said tracking area associated with the second wirelesscommunication system were both indicated in a single received locationupdate message.
 35. The first base station of claim 34, wherein thesingle received location update message is transmitted by the idlemobile unit in response to the idle mobile unit transitioning to thetracking area associated with the second wireless communication system.36. The first base station of claim 34, wherein the first base stationis configured to receive a request to establish an active communicationlink with the first wireless communication system from the idle mobileunit in response to the first base station paging the idle mobile unit,and wherein the first base station is configured to establish the activecommunication link with the mobile unit using a first mobile unitcontext stored on the first wireless communication system, and wherein asecond mobile unit context stored on the second wireless communicationsystem is removed in response to establishing the active communicationlink.
 37. The first base station of claim 34, wherein the first basestation operates according to a 2G/3G radio interface technology or aLong Term Evolution (LTE)/System Architecture Evolution (SAE) radiointerface technology and the second base station operates according tothe other of the LTE/SAE radio interface technology or the 2G/3G radiointerface technology.
 38. A mobile unit configured to register withfirst and second wireless communication systems that operate usingdifferent radio interface technologies, wherein the mobile unit isconfigured to transmit a location update message when the mobile unit isin an idle mode in response to the idle mobile unit transitioningbetween tracking areas associated with one of the first or secondwireless communication systems, and wherein the idle mobile unit remainsassociated with a tracking area that is part of the other one of thefirst and second wireless communication systems after transmitting thelocation update message and the location update message indicates thetracking area transitioned-to and the tracking area associated with saidother of the first and second wireless communication systems.
 39. Themobile unit of claim 38, wherein the mobile unit is configured totransmit the location update message via said one of the first andsecond wireless communication systems in response to the idle mobileunit selecting a base station in a tracking area associated with saidone of the first and second wireless communication systems, and whereinthe mobile unit is further configured to: transmit a request toestablish an active communication link with either of the first andsecond wireless communication systems; and establish the activecommunication link with a wireless communication system indicated in therequest based on a context stored in the wireless communication systemindicated in the request.
 40. A mobile unit configured to register withfirst and second wireless communication systems that operate usingdifferent radio interface technologies, wherein the mobile unit isconfigured to transmit, when it is in idle mode, a location updatemessage in response to the mobile unit transitioning between trackingareas both of which are associated with only one of the first or secondwireless communication systems, the message indicating the tracking areatransitioned-to and the tracking area that is part of the other one ofthe first and second wireless communication systems and being adaptedfor use by the first and second communication systems to keep the idlemobile unit associated with both of the tracking areas that are locatedin the location update message after transmission of the location updatemessage.
 41. A mobile unit configured to register with a first wirelesscommunication system that operates using a second generation(2G)/third-generation (3G) radio interface technology and a secondwireless communication system that operates using a Long Term Evolution(LTE)/System Architecture Evolution (SAE) radio interface technology,wherein the mobile unit is further configured to: transmit a locationupdate message when operating in an idle mode, and wherein the locationupdate message is transmitted in response to the idle mobile unittransitioning between two tracking areas that are both associated withonly one of the first or second wireless communication systems, whereinthe location update message is adapted for use by the first and secondcommunication systems to keep the idle mobile unit associated with thetracking area transitioned-to and a tracking area associated with theother one of the first and second wireless communication systems aftertransmitting the location update message and the location update messageindicates the tracking area transitioned-to and the tracking areaassociated with said other one of the first and second wirelesscommunication systems.
 42. The mobile unit of claim 41, wherein themobile unit is configured to transmit the location update message viasaid one of the first and second wireless communication systems inresponse to the idle mobile unit camping in a tracking area associatedwith said one of the first and second wireless communication systems,and wherein the mobile unit is further configured to: transmit a requestto establish an active communication link with either of the first andsecond wireless communication systems; and establish the activecommunication link with a wireless communication system indicated in therequest based on a context stored in the wireless communication systemindicated in the request.
 43. A first base station configured forimplementation in a first wireless communication system that operatesusing a second generation (2G)/third-generation (3G) radio interfacetechnology, wherein the first base station is configured to page an idlemobile unit that is registered with the first wireless communicationsystem and a second wireless communication system that operates using aLong Term Evolution (LTE)/System Architecture Evolution (SAE) radiointerface technology, and wherein the first base station is configuredto page the idle mobile unit substantially concurrently with a secondbase station paging the idle mobile unit, and wherein the second basestation is implemented in the second wireless communication system thatoperates according to the LTE/SAE radio interface technology, andwherein tracking areas associated with the first and second wirelesscommunication systems are both indicated in a single location updatemessage provided by the idle mobile unit in response to the idle mobileunit transitioning between tracking areas associated with at least oneof the first and second wireless communication systems.
 44. A first basestation configured for implementation in a first wireless communicationsystem that operates using a Long Term Evolution (LTE)/SystemArchitecture Evolution (SAE) radio interface technology, wherein thefirst base station is configured to page an idle mobile unit that isregistered with the first wireless communication system and a secondwireless communication system that operates using a second generation(2G)/third-generation (3G) radio interface technology, and wherein thefirst base station is configured to page the idle mobile unitsubstantially concurrently with a second base station paging the idlemobile unit, and wherein the second base station is implemented in thesecond wireless communication system that operates according to the2G/3G radio interface technology, and wherein tracking areas associatedwith the first and second wireless communication systems are bothindicated in a single location update message provided by the idlemobile unit in response to the idle mobile unit transitioning betweentracking areas associated with at least one of the first and secondwireless communication systems.